A known printing head voltage controller lowers a main voltage output from a switching power supply apparatus by using a printing head voltage control circuit to obtain driving voltages on which a plurality of printing heads operate. This type of voltage controller uses an inexpensive three-terminal regulator in the printing head voltage control circuit. To obtain a stable output, a voltage difference between the IN terminal and OUT terminal of the three-terminal regulator is set to a fixed voltage (1.5 V, for example) or higher.